In recent years, there is a tendency that output of the vehicle AC generator is becoming higher due to increased demands of electronic devices in a vehicle. A high output of the vehicle AC generator increases an output current and thereby increases the amount of heat of components thereof, which results in reducing a quality service life due to a temperature rise.
In particular, a rectifier element rectifying an alternating current generated by the vehicle AC generator is significantly affected by the temperature due to heating, and when the temperature becomes higher than a heat resistance temperature, the service life thereof is reduced sharply.
Further, in recent years, ambient temperature around a vehicle AC generator mounted in a vehicle tends to increase due to the space saving of the engine room. Consequently, increase in the amount of heat and the temperature reduction by improving the cooling performance of the rectifier element has become important problems.
Under such circumstances, Patent Literature 1 proposes a method for improving the cooling efficiency of the rectifier device, which efficiently takes in and flows an external cooling air into a space between positive rectifier elements (positive arm) and a protective cover and into a space between a rear frame and a second heat dissipating plate of negative rectifier elements (negative arm) to increase the cooling efficiency of heat dissipating plates and thereby reduce temperature of rectifier elements.